Comparing Two Arrays in JavaScript

Comparing two arrays in JavaScript looks easy, but it is not as easy as you think. It becomes difficult due to the JavaScript nature of handling objects and references. Besides the primitive data types (like numbers or strings), arrays are the reference data types in JavaScript, which means that if two arrays have the same elements but have a different reference or memory location, they are not considered to be equal.

In this blog, you will explore different methods to compare the arrays in JavaScript, their advantages, and best practices to know the best way to compare two arrays in JavaScript.

Table of Contents:

• Method to Compare Two Arrays in JavaScript
  • Method 1: Using JSON.stringify() Method
  • Method 2: Using a for Loop
  • Method 3: Using join() Method
  • Method 4: Using Array.prototype.every() Method
  • Method 5: Using Lodash Library
  • Method 6: Using a Set for Unordered Comparison
  • Method 7: Using Sorting and Comparison
• Performance Comparison
• Real-World Use Cases
• Conclusion

Method to Compare Two Arrays in JavaScript

JavaScript provides various methods to compare two arrays. Let us discuss each of the methods one by one in detail:

Method 1: Using JSON.stringify() Method

It is one of the simplest ways to compare arrays in JavaScript. You can first convert them into JSON strings and check whether the resulting strings are equal or not. It returns an answer in the form of true or false.

Example:

Output:

Explanation: In this example, you are using JSON.stringify() for comparing arrays. It has simple and more readable syntax.

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Method 2: Using a for Loop

The for loop is a more traditional method for comparing two arrays. It involves checking each element one by one from both arrays.

Example:

Output:

Explanation: In this example, a traditional for loop is used to compare the two arrays. First, it checks for the length of both arrays; if they are not equal, then it returns “Not Equal”. But, if they are equal, then the for loop iterates over each element of the array and compares every element.

Method 3: Using join() Method

The join() method converts an array to a string, and after doing this conversion, we can do a simple comparison between the two strings.

Example:

Output:

Explanation: The join() method also converts an array into a string and then checks for the equality of both strings. If it is found equal, then return true. Otherwise, return false.

Method 4: Using Array.prototype.every() Method

This method checks that every element of one array matches the corresponding elements of the second array.

Example:

Output:

Explanation: In this example, the Array.prototype.every() method checks each element in the array using its index (idx) and prints the output in the form of true or false.

Method 5: Using Lodash Library

For comparing nested arrays (deep comparison), the .isEqual() method from the Lodash library is used.

Example:

Output:

Explanation: An External library like Lodash, which is used for comparing arrays in JavaScript.If arrays contain nested arrays, then using the .isEqual() method of the Lodash library is the best choice.

Method 6: Using a Set for Unordered Comparison

An unordered comparison means comparing the elements without thinking about the order in which the elements are compared, and a Set allows you to compare arrays without considering element order.

Example:

Output:

Explanation: In this example, the Set method is used to convert an array into a set, then after converting it into a set, JavaScript performs the comparison.

Method 7: Using Sorting and Comparison

Sorting both arrays before comparing them is another method for comparing arrays in JavaScript, but this is difficult and least recommended because you need to write extra code for sorting the arrays.

Example:

Output:

Explanation: In this example, the arr.slice().sort() is used for sorting the array, then .join() method is used for converting it into a string and performing comparison.

Performance Comparison

Here is the performance comparison between all the methods used for comparing two objects in JavaScript:

Real-World Use Cases

• Validating User Input: Comparing two arrays in JavaScript is helpful in comparing user-selected options with stored choices.
• API Response Comparison: Checking the output responses of the APIs helps in making the comparison.
• Shopping Cart Updates: Used for detecting changes in cart items.

Conclusion

Comparing two arrays in JavaScript is not an easy task. But JavaScript offers various methods to do so. If you need a fast check, then JSON.stringify() or join() is a good choice. For deep comparison(comparing nested arrays), Lodash’s .isEqual() method is the best option. And if order does not matter, sorting or using a set is helpful. Choosing the right method can help you to compare arrays efficiently.

Comparing Two Arrays in JavaScript – FAQs